Various printing processes in which a substrate is processed by a fuser unit often involve applying a release agent such as an oil to a substrate upon which an image is printed to aid in stripping the substrate from a fuser roll, for example, and/or to protect the fuser roll from contaminants. The application of release agent often results in increased usage life of a fuser roll and reduced contamination compared to an untreated fuser roll. The application of release agent is also often applied to prevent image offset that may occur. Image offset often occurs from the printed substrate to various parts of printing apparatuses and/or finishing equipment such as, but not limited to, rollers, photoreceptor belts, winders, unwinders, die cutters, buffers, stackers, back sides of rolled and/or stacked printed substrates, etc.
Conventionally, a release agent application module that may be part of a fuser unit applies a thin layer of oil to a fuser roll, for example, to enable the substrate to strip from the fuser roll when exiting a fuser portion of the fuser unit. While oil works well as a lubricant, aids in stripping the paper from the fuser roll, and reduces any amounts of contaminants that may stick to the fuser roll, oil can also be carried back to a photoreceptor belt, and cause image related defects.
Various conventional fuser units often offer both simplex and duplex printing job type options. For example, simplex printing refers to a printing process in which a substrate having a first surface and a second surface has an image printed on only one of the first surface and the second surface. Duplex printing refers to a printing process in which a substrate having a first surface and a second surface has an image printed on both the first surface and the second surface.
Conventional fuser units are configured to flood coat the first surface and/or the second surface, as instructed, with a same amount of release agent, regardless of whether the substrate is subjected to a simplex or duplex printing process. Such flood coating of both surfaces often results in excessive amounts of release agent being carried back to unwanted portions of the fuser unit, resulting in various image defects, as discussed above.